/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef nsHtml5String_h
#define nsHtml5String_h
#include "nsAtom.h"
#include "nsString.h"
namespace mozilla {
class StringBuffer;
}
class nsHtml5TreeBuilder;
/**
* A pass-by-value type that can represent
* * nullptr
* * empty string
* * Non-empty string as exactly-sized (capacity is length) `StringBuffer*`
* * Non-empty string as an nsAtom*
*
* Holding or passing this type is as unsafe as holding or passing
* `StringBuffer*`/`nsAtom*`.
*/
class nsHtml5String final {
private:
static const uintptr_t kKindMask = uintptr_t(
3);
static const uintptr_t kPtrMask = ~kKindMask;
enum Kind : uintptr_t {
eNull =
0,
eEmpty =
1,
eStringBuffer =
2,
eAtom =
3,
};
inline Kind GetKind()
const {
return (Kind)(mBits & kKindMask); }
public:
inline bool IsAtom()
const {
return GetKind() == eAtom; }
inline bool IsStringBuffer()
const {
return GetKind() == eStringBuffer; }
inline mozilla::StringBuffer* AsStringBuffer()
const {
MOZ_ASSERT(IsStringBuffer());
return reinterpret_cast<mozilla::StringBuffer*>(mBits & kPtrMask);
}
// DANGER: Calling this is only valid if this is a logically owning
// nsHtml5String and calling Release would be valid.
inline already_AddRefed<mozilla::StringBuffer> ForgetStringBuffer() {
already_AddRefed<mozilla::StringBuffer> ret(AsStringBuffer());
mBits = eNull;
return ret;
}
inline nsAtom* AsAtom()
const {
MOZ_ASSERT(IsAtom());
return reinterpret_cast<nsAtom*>(mBits & kPtrMask);
}
// DANGER: Calling this is only valid if this is a logically owning
// nsHtml5String and calling Release would be valid.
inline already_AddRefed<nsAtom> ForgetAtom() {
already_AddRefed<nsAtom> ret(AsAtom());
mBits = eNull;
return ret;
}
private:
inline const char16_t* AsPtr()
const {
switch (GetKind()) {
case eStringBuffer:
return reinterpret_cast<char16_t*>(AsStringBuffer()->Data());
case eAtom:
return AsAtom()->GetUTF16String();
default:
return nsCharTraits<char16_t>::sEmptyBuffer;
}
}
public:
/**
* Default constructor.
*/
inline nsHtml5String() : nsHtml5String(nullptr) {}
/**
* Constructor from nullptr.
*/
inline MOZ_IMPLICIT nsHtml5String(decltype(nullptr)) : mBits(eNull) {}
inline uint32_t Length()
const {
switch (GetKind()) {
case eStringBuffer:
return (AsStringBuffer()->StorageSize() /
sizeof(char16_t) -
1);
case eAtom:
return AsAtom()->GetLength();
default:
return 0;
}
}
/**
* False iff the string is logically null
*/
inline MOZ_IMPLICIT
operator bool()
const {
return mBits; }
/**
* Get the underlying nsAtom* or nullptr if this nsHtml5String
* does not hold an atom.
*/
inline nsAtom* MaybeAsAtom() {
if (IsAtom()) {
return AsAtom();
}
return nullptr;
}
void ToString(nsAString& aString);
// Same output as above, but this string is logically null afterwards.
// Avoids an AddRef if this string is holding a StringBuffer.
// DANGER: Use this only on an instance that is logically an
// owning instance and `Release()` would be valid to call!
void MoveToString(nsAString& aString);
void CopyToBuffer(char16_t* aBuffer)
const;
bool LowerCaseEqualsASCII(
const char* aLowerCaseLiteral)
const;
bool EqualsASCII(
const char* aLiteral)
const;
bool LowerCaseStartsWithASCII(
const char* aLowerCaseLiteral)
const;
bool Equals(nsHtml5String aOther)
const;
nsHtml5String Clone();
void Release();
static nsHtml5String FromBuffer(char16_t* aBuffer, int32_t aLength,
nsHtml5TreeBuilder* aTreeBuilder);
static nsHtml5String FromLiteral(
const char* aLiteral);
static nsHtml5String FromString(
const nsAString& aString);
static nsHtml5String FromAtom(already_AddRefed<nsAtom> aAtom);
static nsHtml5String FromStaticAtom(nsStaticAtom* aAtom);
static nsHtml5String EmptyString();
private:
/**
* Constructor from raw bits.
*/
explicit nsHtml5String(uintptr_t aBits) : mBits(aBits) {};
/**
* Zero if null, one if empty, otherwise tagged pointer
* to either nsAtom or nsStringBuffer. The two least-significant
* bits are tag bits.
*/
uintptr_t mBits;
};
#endif // nsHtml5String_h
